In recent years, with the growth of the print-on-demand market, the demands for speeding up electrophotographic techniques are all the more increasing. In view of the above, as a means for meeting the requirement of speeding up, a toner that is capable of fixing at a low temperature is studied in order to fix the toner on paper with less energy. For example, a toner having excellent low-temperature fixing ability by containing a linear low-softening point polyester as a resin binder (see JP-A-Hei-3-5764 (U.S. Pat. No. 5,079,123), JP-A-Hei-6-282102 (U.S. Pat. No. 5,395,726), and the like); a method for producing a toner including the step of melt-kneading under specified conditions, using a resin binder containing a polyester having a softening point of from 90° to 110° C. and a low-melting point wax having a melting point of from 60° to 90° C. (see JP-A-2006-47879, and the like); and the like are proposed.
Further, in order to control an increase in toner scattering, i.e. toner dust, caused by the speeding up of a developer device, a polyester having a high triboelectric chargeability obtained from an aromatic monomer such as terephthalic acid as a raw material monomer for a resin binder is widely used. In addition, with the speeding up, mechanical stress applied to a toner also increases, so that durability is lowered; however, by using the above aromatic monomer, the glass transition temperature of the polyester is increased, and durability is also increased (see JP-A-2003-149865, and the like).
On the other hand, as a new charge control agent having a quick initial rise of triboelectric charges and excellent environmental stability, a specified azo-iron complex is reported in JP-A-2007-334139.